1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Microchip / Atmel ECC (I2C) driver. 4 * 5 * Copyright (c) 2017, Microchip Technology Inc. 6 * Author: Tudor Ambarus <tudor.ambarus@microchip.com> 7 */ 8 9 #include <linux/bitrev.h> 10 #include <linux/crc16.h> 11 #include <linux/delay.h> 12 #include <linux/device.h> 13 #include <linux/err.h> 14 #include <linux/errno.h> 15 #include <linux/i2c.h> 16 #include <linux/init.h> 17 #include <linux/kernel.h> 18 #include <linux/module.h> 19 #include <linux/scatterlist.h> 20 #include <linux/slab.h> 21 #include <linux/workqueue.h> 22 #include "atmel-i2c.h" 23 24 /** 25 * atmel_i2c_checksum() - Generate 16-bit CRC as required by ATMEL ECC. 26 * CRC16 verification of the count, opcode, param1, param2 and data bytes. 27 * The checksum is saved in little-endian format in the least significant 28 * two bytes of the command. CRC polynomial is 0x8005 and the initial register 29 * value should be zero. 30 * 31 * @cmd : structure used for communicating with the device. 32 */ 33 static void atmel_i2c_checksum(struct atmel_i2c_cmd *cmd) 34 { 35 u8 *data = &cmd->count; 36 size_t len = cmd->count - CRC_SIZE; 37 u16 *__crc16 = (u16 *)(data + len); 38 39 *__crc16 = cpu_to_le16(bitrev16(crc16(0, data, len))); 40 } 41 42 void atmel_i2c_init_read_cmd(struct atmel_i2c_cmd *cmd) 43 { 44 cmd->word_addr = COMMAND; 45 cmd->opcode = OPCODE_READ; 46 /* 47 * Read the word from Configuration zone that contains the lock bytes 48 * (UserExtra, Selector, LockValue, LockConfig). 49 */ 50 cmd->param1 = CONFIG_ZONE; 51 cmd->param2 = DEVICE_LOCK_ADDR; 52 cmd->count = READ_COUNT; 53 54 atmel_i2c_checksum(cmd); 55 56 cmd->msecs = MAX_EXEC_TIME_READ; 57 cmd->rxsize = READ_RSP_SIZE; 58 } 59 EXPORT_SYMBOL(atmel_i2c_init_read_cmd); 60 61 void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid) 62 { 63 cmd->word_addr = COMMAND; 64 cmd->count = GENKEY_COUNT; 65 cmd->opcode = OPCODE_GENKEY; 66 cmd->param1 = GENKEY_MODE_PRIVATE; 67 /* a random private key will be generated and stored in slot keyID */ 68 cmd->param2 = cpu_to_le16(keyid); 69 70 atmel_i2c_checksum(cmd); 71 72 cmd->msecs = MAX_EXEC_TIME_GENKEY; 73 cmd->rxsize = GENKEY_RSP_SIZE; 74 } 75 EXPORT_SYMBOL(atmel_i2c_init_genkey_cmd); 76 77 int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd, 78 struct scatterlist *pubkey) 79 { 80 size_t copied; 81 82 cmd->word_addr = COMMAND; 83 cmd->count = ECDH_COUNT; 84 cmd->opcode = OPCODE_ECDH; 85 cmd->param1 = ECDH_PREFIX_MODE; 86 /* private key slot */ 87 cmd->param2 = cpu_to_le16(DATA_SLOT_2); 88 89 /* 90 * The device only supports NIST P256 ECC keys. The public key size will 91 * always be the same. Use a macro for the key size to avoid unnecessary 92 * computations. 93 */ 94 copied = sg_copy_to_buffer(pubkey, 95 sg_nents_for_len(pubkey, 96 ATMEL_ECC_PUBKEY_SIZE), 97 cmd->data, ATMEL_ECC_PUBKEY_SIZE); 98 if (copied != ATMEL_ECC_PUBKEY_SIZE) 99 return -EINVAL; 100 101 atmel_i2c_checksum(cmd); 102 103 cmd->msecs = MAX_EXEC_TIME_ECDH; 104 cmd->rxsize = ECDH_RSP_SIZE; 105 106 return 0; 107 } 108 EXPORT_SYMBOL(atmel_i2c_init_ecdh_cmd); 109 110 /* 111 * After wake and after execution of a command, there will be error, status, or 112 * result bytes in the device's output register that can be retrieved by the 113 * system. When the length of that group is four bytes, the codes returned are 114 * detailed in error_list. 115 */ 116 static int atmel_i2c_status(struct device *dev, u8 *status) 117 { 118 size_t err_list_len = ARRAY_SIZE(error_list); 119 int i; 120 u8 err_id = status[1]; 121 122 if (*status != STATUS_SIZE) 123 return 0; 124 125 if (err_id == STATUS_WAKE_SUCCESSFUL || err_id == STATUS_NOERR) 126 return 0; 127 128 for (i = 0; i < err_list_len; i++) 129 if (error_list[i].value == err_id) 130 break; 131 132 /* if err_id is not in the error_list then ignore it */ 133 if (i != err_list_len) { 134 dev_err(dev, "%02x: %s:\n", err_id, error_list[i].error_text); 135 return err_id; 136 } 137 138 return 0; 139 } 140 141 static int atmel_i2c_wakeup(struct i2c_client *client) 142 { 143 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); 144 u8 status[STATUS_RSP_SIZE]; 145 int ret; 146 147 /* 148 * The device ignores any levels or transitions on the SCL pin when the 149 * device is idle, asleep or during waking up. Don't check for error 150 * when waking up the device. 151 */ 152 i2c_master_send(client, i2c_priv->wake_token, i2c_priv->wake_token_sz); 153 154 /* 155 * Wait to wake the device. Typical execution times for ecdh and genkey 156 * are around tens of milliseconds. Delta is chosen to 50 microseconds. 157 */ 158 usleep_range(TWHI_MIN, TWHI_MAX); 159 160 ret = i2c_master_recv(client, status, STATUS_SIZE); 161 if (ret < 0) 162 return ret; 163 164 return atmel_i2c_status(&client->dev, status); 165 } 166 167 static int atmel_i2c_sleep(struct i2c_client *client) 168 { 169 u8 sleep = SLEEP_TOKEN; 170 171 return i2c_master_send(client, &sleep, 1); 172 } 173 174 /* 175 * atmel_i2c_send_receive() - send a command to the device and receive its 176 * response. 177 * @client: i2c client device 178 * @cmd : structure used to communicate with the device 179 * 180 * After the device receives a Wake token, a watchdog counter starts within the 181 * device. After the watchdog timer expires, the device enters sleep mode 182 * regardless of whether some I/O transmission or command execution is in 183 * progress. If a command is attempted when insufficient time remains prior to 184 * watchdog timer execution, the device will return the watchdog timeout error 185 * code without attempting to execute the command. There is no way to reset the 186 * counter other than to put the device into sleep or idle mode and then 187 * wake it up again. 188 */ 189 int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd) 190 { 191 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); 192 int ret; 193 194 mutex_lock(&i2c_priv->lock); 195 196 ret = atmel_i2c_wakeup(client); 197 if (ret) 198 goto err; 199 200 /* send the command */ 201 ret = i2c_master_send(client, (u8 *)cmd, cmd->count + WORD_ADDR_SIZE); 202 if (ret < 0) 203 goto err; 204 205 /* delay the appropriate amount of time for command to execute */ 206 msleep(cmd->msecs); 207 208 /* receive the response */ 209 ret = i2c_master_recv(client, cmd->data, cmd->rxsize); 210 if (ret < 0) 211 goto err; 212 213 /* put the device into low-power mode */ 214 ret = atmel_i2c_sleep(client); 215 if (ret < 0) 216 goto err; 217 218 mutex_unlock(&i2c_priv->lock); 219 return atmel_i2c_status(&client->dev, cmd->data); 220 err: 221 mutex_unlock(&i2c_priv->lock); 222 return ret; 223 } 224 EXPORT_SYMBOL(atmel_i2c_send_receive); 225 226 static void atmel_i2c_work_handler(struct work_struct *work) 227 { 228 struct atmel_i2c_work_data *work_data = 229 container_of(work, struct atmel_i2c_work_data, work); 230 struct atmel_i2c_cmd *cmd = &work_data->cmd; 231 struct i2c_client *client = work_data->client; 232 int status; 233 234 status = atmel_i2c_send_receive(client, cmd); 235 work_data->cbk(work_data, work_data->areq, status); 236 } 237 238 void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data, 239 void (*cbk)(struct atmel_i2c_work_data *work_data, 240 void *areq, int status), 241 void *areq) 242 { 243 work_data->cbk = (void *)cbk; 244 work_data->areq = areq; 245 246 INIT_WORK(&work_data->work, atmel_i2c_work_handler); 247 schedule_work(&work_data->work); 248 } 249 EXPORT_SYMBOL(atmel_i2c_enqueue); 250 251 static inline size_t atmel_i2c_wake_token_sz(u32 bus_clk_rate) 252 { 253 u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC); 254 255 /* return the size of the wake_token in bytes */ 256 return DIV_ROUND_UP(no_of_bits, 8); 257 } 258 259 static int device_sanity_check(struct i2c_client *client) 260 { 261 struct atmel_i2c_cmd *cmd; 262 int ret; 263 264 cmd = kmalloc(sizeof(*cmd), GFP_KERNEL); 265 if (!cmd) 266 return -ENOMEM; 267 268 atmel_i2c_init_read_cmd(cmd); 269 270 ret = atmel_i2c_send_receive(client, cmd); 271 if (ret) 272 goto free_cmd; 273 274 /* 275 * It is vital that the Configuration, Data and OTP zones be locked 276 * prior to release into the field of the system containing the device. 277 * Failure to lock these zones may permit modification of any secret 278 * keys and may lead to other security problems. 279 */ 280 if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) { 281 dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n"); 282 ret = -ENOTSUPP; 283 } 284 285 /* fall through */ 286 free_cmd: 287 kfree(cmd); 288 return ret; 289 } 290 291 int atmel_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id) 292 { 293 struct atmel_i2c_client_priv *i2c_priv; 294 struct device *dev = &client->dev; 295 int ret; 296 u32 bus_clk_rate; 297 298 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { 299 dev_err(dev, "I2C_FUNC_I2C not supported\n"); 300 return -ENODEV; 301 } 302 303 bus_clk_rate = i2c_acpi_find_bus_speed(&client->adapter->dev); 304 if (!bus_clk_rate) { 305 ret = device_property_read_u32(&client->adapter->dev, 306 "clock-frequency", &bus_clk_rate); 307 if (ret) { 308 dev_err(dev, "failed to read clock-frequency property\n"); 309 return ret; 310 } 311 } 312 313 if (bus_clk_rate > 1000000L) { 314 dev_err(dev, "%d exceeds maximum supported clock frequency (1MHz)\n", 315 bus_clk_rate); 316 return -EINVAL; 317 } 318 319 i2c_priv = devm_kmalloc(dev, sizeof(*i2c_priv), GFP_KERNEL); 320 if (!i2c_priv) 321 return -ENOMEM; 322 323 i2c_priv->client = client; 324 mutex_init(&i2c_priv->lock); 325 326 /* 327 * WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate - 328 * 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz 329 * will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE. 330 */ 331 i2c_priv->wake_token_sz = atmel_i2c_wake_token_sz(bus_clk_rate); 332 333 memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token)); 334 335 atomic_set(&i2c_priv->tfm_count, 0); 336 337 i2c_set_clientdata(client, i2c_priv); 338 339 ret = device_sanity_check(client); 340 if (ret) 341 return ret; 342 343 return 0; 344 } 345 EXPORT_SYMBOL(atmel_i2c_probe); 346 347 MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>"); 348 MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver"); 349 MODULE_LICENSE("GPL v2"); 350